Houdan eggs not hatching

[Chicks123456789]

For the past three or so hatches, I have had all of my houdan eggs grow perfectly until day 21, then they just die. Meanwhile, on every one of those hatches, I have had 20+ brahma chicks hatch each time without being shrink wrapped or sticky. This past hatch which was yesterday, I had one houdan pip but it died some time later. Why won’t my houdans hatch but my brahmas will? The houdan eggs are very large while the brahma eggs are relatively small which most likely has something to do with it. These eggs are all from my own flock. Do the houdan eggs take longer to grow, and should I put them in a day or two before the brahma eggs? I hatched over 50 houdans this past august with no problems but this year they will not hatch. I am using a hovabator 1588, very reliable and no temp fluctuations. I keep the humidity between 30-45 for the first 18 days and 60+ the last few days. I keep the temp at 100.5, in a relatively room temperature room. I do not know why these houdan eggs are not hatching when i hatched so many of them last year. My houdan hen and rooster are 2+ years old if that has something to do with it. Thanks

 

[SmiYa0126]

@Kiki any ideas?

 

[Kiki]

Do you have a calibrated thermometer in your bator?

 

[Chicks123456789]

Do you have a calibrated thermometer in your bator?

No, but i checked the temp on a regular baking thermometer and it was the right temp

 

[Kiki]

No, but i checked the temp on a regular baking thermometer and ot was the right temp

Get one or three of these and you will know for sure.
https://www.amazon.com/Govee-Hygrom...f56346d386688e146851b26525a&gad_source=1&th=1

 

[Chicks123456789]

Get one or three of these and you will know for sure.
https://www.amazon.com/Govee-Hygrom...f56346d386688e146851b26525a&gad_source=1&th=1

I checked on a few different thermometers and they were all within the 100-100.5 range

 

[Chicks123456789]

But it wouldn’t be a temp issue if i hatched 35 eggs in the same incubator at the exact same time as the houdan eggs would it? And i opened some of the houdan eggs and they were fully developed, yolk gone and in hatching position

 

[Kiki]

But it wouldn’t be a temp issue if i hatched 35 eggs in the same incubator at the exact same time as the houdan eggs would it? And i opened some of the houdan eggs and they were fully developed, yolk gone and in hatching position

Did you have the eggs separated....each type on one side of the bator?

 

[Chicks123456789]

Did you have the eggs separated....each type on one side of the bator?

Yeah I have had them on opposite sides of the incubator and I always put the houdan eggs closest to the front…